1. Field of the Invention
This invention relates to a novel magnetic recording apparatus and a magnetic head used therein.
2. Description of the Prior Art
The technique of recording electric signals on a magnetic recording medium in the form of residual magnetism is now in progress along with the development of recording mediums such as magnetic tapes and magnetic discs. The apparatuses using these recording mediums are largely classified into a magnetic recording apparatus and an opto-magnetic recording apparatus according to the recording method employed. The magnetic recording is accomplished by applying a magnetic field by means of a magnetic head to a narrow region of the recording medium where the temperature is lower than the Curie point and forcibly reversing the positive and negative polarities of the spontaneous magnetization inherent in a ferromagnetic material. The opto-magnetic recording on the other hand is done by radiating a beam of light such as laser onto a narrow region on a ferromagnetic material to raise the temperature of that region above the Curie point and thereby reverse the spontaneous magnetization. Another method is also used in which a weak magnetic field is applied in addition to the laser beam to assist the reversal of the spontaneous magnetization. These recording methods differ in the recording density and the recording and playback speeds. As to the recording density, because one reversed region of spontaneous magnetization constitutes the unit of recording, the recording density depends on the size of the reversed region. The smaller the reversed region, the greater the recording density will become. The size of the reversed region in the magnetic recording is determined by the spreading of the flux generated by the magnetic head. The size of the reversed region in the opto-magnetic recording is determined by an extent to which the irradiated laser beam is focused. The currently available technology reduces the size of the reversed region in the opto-magnetic recording to the order of 0.1 .mu.m, about one order smaller than the reversed region size in the magnetic recording. This means that the recording density for the opto-magnetic recording is significantly higher than for the magnetic recording. The recording and playback speed depends on the reversing speed of the spontaneous magnetization and the moving speed of the magnetic head or the light irradiation head. Since the magnetic recording has higher reversing speed and head moving speed than the opto-magnetic recording, the magnetic recording is remarkably advantageous over the opto-magnetic recording in terms of the recording and playback speed.
JP-A-63-259808 and JP-A-63-313305 disclose that magnetic recording of high density is effected by surrounding magnetic poles of the magnetic head with a superconductive material of oxide system to prevent leakage of flux from the sides of the magnetic poles and spreading of flux in a space at the front ends of the magnetic poles. However, this method does not recognize the fact that the flux does not pass through the inside of the superconductive material surrounding the magnetic poles. Accordingly, if the flux is forcibly passed through the inside of the superconductive material, an eddy current is caused to flow in the superconductive material provided around the magnetic poles to impede the passage of the flux and the superconductive material loses its superconductive characteristics. As a result, the effect of preventing the spreading and leakage of the flux cannot be obtained.